Stroke-prone spontaneously hypertensive rats (SHRSP) established by Okamoto, Yamori and Nagaoka (1973) are maintained to keep the high incidence of stroke over 80% and are used for the studies on the pathogenesis and prophylaxis of stroke in comparison with stroke-resistant SHR (SHRSR) in which the incidence of stroke is less than 10%. (a) Studies on the SHRSP: (1) The further continuation of selective breeding of SHRSP to maintain the concentrated genetic disposition of stroke. (2) Genetic analysis of stroke is continued by observing the incidence of stroke in F1, F2 and back cross generations obtained from crosses between SHRSP and SHRSR or normotensive rats. (3) Symptomatology, behavior, blood pressure, blood chemistry and electroencephalography are studied in SHRSP to establish the measures for the prescience of stroke. (4) Systemic factors of stroke are studied especially on the humoral factors related to stroke and platelet function, and also on physico-chemical characteristics of arterial walls. (5) Local factors of stroke are further studied by observing regional cerebral blood flow through the implanted electrodes at the predilection sites of stroke. (6) Prophylactic effects on strlke are studied not only by controlling nutritional conditions such as protein, lipid and various vitamin concentrations. (b) Studies on the other hypertensive sequelae in SHR: (1) The further continuation of selective breeding of SHR which show hypercholesterolemic response when fed on high fat-cholesterol diet. (2) Atherogenesis in these SHR is studied on the pathogenesis, especially from functional and biochemical aspects. (3) Prevention of cerebrovascular sclerosis and systemic arteriosclerosis is studied in these SHR. (4) Myocardial lesions in SHRSP and other SHR substrains under different nutritional conditions is studied to evaluate the interaction between genetic disposition and environmental factors in the development of hypertension sequelae. BIBLIOGRAPHIC REFERENCES: Okamoto, K., Hazama, F., Yamori, Y., Haebara, H. and Nagaoka, A.: Pathogenesis and prevention of stroke in spontaneously hypertensive rats. Clin. Sci. Mol. Med., 48, 161s-163s, 1975.